Open AccessJournal Article
Release of medroxyprogesterone acetate from a silicone polymer.
T. J. Roseman,William I. Higuchi +1 more
TLDR
In this paper, the physicochemical factors involved in the in vitro release of medroxyprogesterone acetate (MPA) a water-insoluble steroid embedded in a silicone rubber matrix was based upon a model system which considered the matric boundary diffusion layer.Abstract:
A study of the physicochemical factors involved in the in vitro release of medroxyprogesterone acetate (MPA) a water-insoluble steroid embedded in a silicone rubber matrix was based upon a model system which considered the matric boundary diffusion layer; extensive mathematical equations for the model are presented for planar and cylindrical cases. Initial and long-time release rates were obtained. Zones of MPA depletion were measured microscopically as a function of time and the partition coefficient of MPA was determined. Following relatively constant initial release rates a nonlinear dependence of release rates upon MPA concentration (3% 12% 24%) was found. As MPA diffused from the matrix well-defined zones of depletion developed and were photographed. Comparison of the present model to the T. Higuchi model of drug release (based on a purely matrix-controlled system) indicated that when boundary layer was considered a better fit of experimental data to theory was found. Findings suggest that the partition coefficient diffusion coefficients medroxyprogesterone acetate concentration within the polymer and agitation conditions play important roles in the release process. The applicability of the model to an in vivo system (in which slower release of MPA has been observed) is evaluated.read more
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Membrane Technology and Applications
TL;DR: Overview of membrane science and technology membrane transport theory membrane and modules concentration polarization reverse osmosis ultrafiltration microfiltration gas separation pervaporation ion exchange membrane processes - electrodialysis carrier facilitated transport medical applications of membranes other membranes processed.
Journal ArticleDOI
A simple equation for description of solute release I. Fickian and non-fickian release from non-swellable devices in the form of slabs, spheres, cylinders or discs
TL;DR: In this paper, a simple exponential relation Mt/M∞ = ktn is introduced to describe the general solute release behavior of controlled release polymeric devices, where Mt is the fractional release, t is the release time, k is a constant, and n is the diffusional exponent characteristic of the release mechanism.
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Degradable Controlled-Release Polymers and Polymeric Nanoparticles: Mechanisms of Controlling Drug Release
Journal ArticleDOI
On the importance and mechanisms of burst release in matrix-controlled drug delivery systems
Xiao Huang,Christopher S. Brazel +1 more
TL;DR: Experimental observations of burst release in monolithic polymer controlled drug delivery systems, theories of the physical mechanisms causing burst, some of the unique ideas used to prevent burst, and the treatment of burstRelease in controlled release models are reviewed.
Journal ArticleDOI
Higuchi equation: derivation, applications, use and misuse.
TL;DR: The aim of this review is to highlight the assumptions the derivation of the classical Higuchi equation is based on and to give an overview on the use and potential misuse of this equation as well as of related theories.
References
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Book ChapterDOI
Controlled Release of Biologically Active Agents
TL;DR: A recent innovation is the use of biodegradable polymers such as polylactic acid (PLA), which will also assure a complete delivery of the drug.
Journal ArticleDOI
Monte Carlo simulations and fractional kinetics considerations for the Higuchi equation.
TL;DR: The application of the Higuchi equation to different geometries is discussed and Monte Carlo simulations to verify the validity of Higuchi law in one and two dimensions, as well as the derivation of theHiguchi equation under alternative boundary conditions making use of fractional calculus are presented.
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Controlled release of levamisole from poly-(E-caprolactone) matrices: III. Effects of molecular weight and polymer coating on drug release
Th.F. Vandamme,J.-F. N. Mukendi +1 more
TL;DR: In this paper, the influence of the molecular weight of the poly-(epsilon-caprolactone) (PCL) constituting the polymeric matrix and the effect of coatings on selected Rumino-reticulum devices (RRDs) was studied by the rate and the kinetic release of a model anthelmintic compound.
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Kinetics of release of a model disperse dye from supersaturated cellulose acetate matrices.
TL;DR: General and early-time approximate expressions based on the Roseman-Higuchi model proved useful for the interpretation of the results in such cases; while the said model was extended to include the effect of significant variation of the partition coefficient of the solute with concentration.
Journal ArticleDOI
Drug release from matrices made of polymers with reacting sites
TL;DR: In this paper, the release of drugs which may interact with the polymer matrix was studied, and the dispersions of each of the two drugs were made with each of methacrylate copolymers, and compressed into tablets.